19.
(a) The calculation of the potential here parallels the calculation of
the potential due to a dipole. Since this time you are to get the
potential on the axis only, the algebra is much simpler and you do not
need to make any approximations. Get an exact answer.
(c) What is the physical meaning of qV(x) ?
20.
(b) You can
either recalculate the field from scratch using Coulomb's Law or you
can use the relation that Ex = - dV(x)/dx [see
text section 25-9]. In the last question, which could have been
called part (c), compare problem 19 part (c).
21. How do you get the potential when there is a continuous distribution of charge?
22. The charges do not wind up all having the same KE. Why not?
23. Get all three components of the field. You might want to look at section 25-9 of the text.
24, 25. In general, if there is enough symmetry that you can use Gauss's Law to get the electric field, the easiest way to get the electric potential is to get the field first and integrate it to get the potential. Sections 25-4 and 25-5 have a discussion of the process, and we will do at least one example in class. #24 is actually harder than #25, so I suggest doing #25 first. You should at least be able to get the potential outside the charge. To get the potential inside, remember that the potential is a continuous function. Its value at r=R can be determined using the field outside the charge distribution. Then you can integrate the field inward from r=R.
| Last revised 3/13/97 |